Iron Out or Super IO works best for eating rust off things. You can buy it at most hardware, big box and grocery stores.

I would have mixed up a few gallons of warm water in a bucket dissolving a cup of IO in it and poured it into the salt tank water and then put the valve into a manual regeneration and sucked it into the resin tank and unplugged the control at the end ot the Brining cycle for a half hour and then plugged it in to finish on it's own. I would have done that before removing anything from the resin tank. That way you clean all the rust off the resin too.

Now you can soak the valve parts in a solution after taking them off/out of the control valve and seting the valve in some too without getting any electrical stuff wet. Bathe the distributor tube with the solution witoput getting any in your eyes and get all the rust out of the bottom basket.

Disinfect wit ha bleach solution AFTER fully rinsing the IO out of/off everything; DO NOT mix the two, that is dangerous.

And when all is back together, use a 1/4 cup of IO mixed in a couple gallons of water and do a manual regeneration about once a month and and everything will stay rust free.